The worldwide morbidity, mortality and economic losses caused by rotavirus-induced gastroenteritis have established a need for effective methods of disease prevention and control. This proposal focuses on basic studies on the human rotaviruses, which can now be cultivated in the laboratory. The number of viral serotypes and the antigenic stability of these serotypes will be examined by cultivating and characterizing viruses collected over a 9-year period from widely different geographic locations. Viruses will be characterized systematically using classical neutralization assays with hyperimmune antiserum prepared to prototype viruses. In addition, viruses will be characterized by three independent gene products that are immunologically distinct (two outer capsid proteins, VP3 and VP7, and an inner capsid protein, VP6) to provide direct evidence for gene reassortment as a mechanism of antigenic shift or drift. These studies will utilize monospecific antibodies prepared against the outer capsid proteins of prototype strains and monoclonal antibodies already available to the two types of a subgroup antigen on the inner capsid protein. Stools found to contain rotaviruses initially by electron microscopy will also be analyzed by enzyme-linked immunosorbent assays to screen for new antigenically distinct rotaviruses. Stools containing these viruses will be used to prepare reagents to detect these new agents, and these reagents will be used to gain preliminary information on the prevalence and clinical significance of these new enteric viruses. The potential genetic interaction between antigenically distinct rotaviruses and human and animal rotaviruses that share common antigens will also be evaluated to determine if these different rotaviruses share a gene pool. These studies will also determine if the Rotavirus genus should be divided into subgroups. Finally, the molecular basis for the functioning of the outer capsid protein required for infectivity will be examined through structural studies of VP3. These studies will provide basic knowledge that is required to begin to understand the epidemiology of rotavirus disease and to help develop strategies to prevent this important disease in children and animals.